Attachment for electrical conduits.



A. MGMURTRIE.

ATTACHMENT FOR ELECTRICAL CONDUITS.

APPLIGATION FILED APR. 25, 1907.

@wvo Patented Nov. 15, 1910.

. A Mg aamf.,

UNITE@ STATES PATENT @FFIQE y ADNAH MCMURTRIE, 0F NEW YORK, N. Y., ASSI'GNOR TO THOMAS & BETTS COMPANY,

0F NEW YORK, N. Y., A CORPORATION OF NEW YORK., i

ATTAOHMENT FOR ELECTRICAL CONDUITS.

Specification of Letters Patent.

rai-ente@ Nov. i5, raro.

'their union with outlet boxes or similar electrical conduit members.

My present invention is of they general type of such devices, in which a member is wedged between the armor sheath and the wall of the aperture through which the conductors enter the outlet box; and in accordance with my improvements the wedge is so arranged as to force the sheath into contact with the wall of the aperture, effecting direct physical and electrical union therewith, instead of relying upon the indirect grip of a plurality of lingers which, in the earlier forms of such a device, intervene between the sheath and the wall of the aperture, making a double interruption of the continuity of the path for the electrical current to ground, in emergencies. I avoid also the rotative motion heretofore required in some such devices to fasten the sheath, which motion is not always convenient, and. apertures of special contour are not essential to the use of my improvements, which can be applied to existing structures without modification.

The various features of my invention will be illustrated and described fully in the accompanying drawings and specification and pointed out in the claims.

In the drawings, Figure 1 is a View in vertical section of an outlet box furnished with attachments in the construction of Awhich my invention has been embodied. Fig. 2 is a perspective view of one of the bushings with its wedge, showing the general relation therebetween.

In the embodiment of my invention selected for illustration and description as a convenient form of construction to enable ready and complete understanding of my improvements, referring to the drawings, the lpart designated by the reference numeral 1 is a` wedge member introduced between the wall'2 of the'aperture 3 in the plate 4 constituting the side wall of an electrical outlet box, and an armor sheath 5 passing through the aperture, suitable means 6 being provided to move the wedge co-axially with respect to the sheath, to force the latter into direct physical and electrical contact with the wall ot the aperture. v

The actuating means 6 may take any convenient and suitable form, and is shown as a short screw bolt passing through a plain hole 7 in a lug 8 of the wedge' member, and through a plain hole 9 in the box wall, a nut 10 serving to retain it in adjusted position. This form of wedge member has its surface 11 inclined and can be used readily in the ordinary roundvhole 3 usual to the wellknown type of cast or pressed metal outlet box illustrated, and with any of the tubular armor sheaths known to the trade, whether having a separate identity as conduit into which conductors are fished, vor formed as a unitary structure with the conductors, and thus installed, as in the lead covered cable or the armored conductors, so-called. At 12 a similar wedge member is provided with an actuating screw 13, passing through a plain slot 14 into a threaded hole 15 in the bottom plate or wall 16 of the box near the aperture 17, which may be beveled as shown at 18 to correspond with the cooperating surface 19 o the wedge, the screw lwhen driven home causing co-axial movement of the wedge 12 relatively to the armored conductor sheath 20, and at the same time forcing the sheath into direct physical and electrical contact with the opposite wall of the aperture 17. I have shown this aperture as provided with a housing 21, formed integrally with the bottom of the box, and having a gateway 22 for the wedge, and an annular shoulder 23 to prevent abrasion of the insulation 2li-on the conductors 25. lar housing may be formed integrally, or as a unitary structure, with thewedge membe', as the housing -26 carried by the wedge 27 in the central portion of Fig. 1. A screw 28 may serve as the actuating means in this instance, passing through a slotted lug 29 into a threaded hole 30 in the bottom of the box, and operating in the manner already described to draw the wedge and force the sheath 31 into direct physical'and electrical contact with the opposite wall of the aper- A simiture 32. This aperturemay be .provided ers used in earlier forms of such vdevices or securing the direct engagement between the sheath and aperture wall, in accordance with my improvements.

I have shown a neck 33 in the center of othe box merely becauseone is frequently found there to strengthen the wall of the box'and afford an extended bearing around the central aperture 32 which Ais often used to receive the gas pipe, or to receive a support for the box, as when the box is inverted below a ceiling in a manner readily understood by inverting'the drawing, when the sheath 31 would be seen in place of a support, and not Ainfrequently existing boxes will be found with holes in the region near lthis central aperture, already threaded for the attachment of fixture studs or other deyvices, so that the screw 28 can be seated in one of these without the need for any altera; tion, the lug slotI 29 permitting some adjustment of the 'screw for this purpose, and when open at the outer end, as shown, the lug may be applied to the screw after the latter has been started intothe hole 30.

The attachment illustrated at 43 is substantially the same in construction as that numbered .26 and already described, but its -wedge 44 is somewhat shortened to coperate with the beveled wall 45.0f the aperture 46, where-it isxless convenient to utilize a neck.

Having illustrated' and described thus fully varlous forms ofconstruction'in which my invention maybe `embodied advantageously-,Iit will be understood that l do not limit myself to these specific forms, nor to the specific material mentioned, nor in general otherwise than as set forth in the claims read in connection with this specification.

What I claim as new and desire to secure by Letters Patent is 1. The combination with a plate apertured to pass an electrical conductor and an armor sheath therefor, of an attaching member comprising a wedge and means to move said wedge throu h said plate co-axially with respect to sai sheath to force the latter into binding engagement with the opposite wall of said aperture, substantially as described.

2. An attaching member for the purpose set forth, comprlsing a wedge to enter a -sheath-receiving aperture in an outlet box between said sheath and the wall of said aperture, and means to drive said wedge through said wall co-axially with respect to said sheath, to force said sheath into direct physical and electrical contact with the opposite wall of .said aperture, substantially as described.

3. An attaching member for theipurpose set forth; comprlslng a wedge to enter a sheath-receiving aperture in the wall of an outlet box between said sheath and the wall of said aperture, means to drive said wedge through said wall co-axially with respect to said sheath, to force said sheath into direct physical and electrical contact with the opposite wall of said aperture, and a sheathend-housing carried by said wedge.

.. Signed at New York in thel county and State of New York this sixteenth day of April, 1907.

Y ADNAH MGMURTRIE.

Witnesses: v

ALEXANDER C. PROUDFIT, HoBART W. BETrs. 

